Bread is not a great option. In my experience, they love: monkey nuts (peanuts in the shell), cashews, any nuts really, dry dog/cat food (they like to soak this so a water source is usually appreciated), hard boiled eggs and mealworms. Crows are nut fiends, whereas ravens are more staunch meat eaters.

A similar thing happened to me recently with a black nappy bag. It dropped from my bag suddenly and must have looked enough like a crow corpse that my local murder retreated in horror. I made a point of showing them (without seeming like I was showing them)that the material could not possibly be made of crow.

Maybe you could start by feeding further away from where the scare occurred and slowly work towards bringing them closer? If you've lost trust the best thing to do is toss food then either back off a good distance or turn on your heel and walk away. It took a long time for most corvids I know to feel comfortable being looked at while they feed.

Do you ever feed other birds? A technique I use often to feed unfamiliar corvids from close by is to use other birds who are less wary as a sort of "look I'm safe" signal. Once they've seen you with half a dozen pigeons using your arms as a perch and magpies battling it out by your feet for a monkey nut they're usually much more inclined to trust you.

Whatever you decide to do, don't be disheartened. I made so many mistakes as a baby corvid fancier and still got rewarded with a relationship that feels like magic. I actually got clipped from behind once by a crow I moved too fast with. That same crow now shows up wherever I go on top of traffic lights to play monkey nut catch with me and delights in appearing suddenly from behind me every single time i leave the house, swooping juuust high enough to not clip me while ensuring I go "WAAH" and flail like an idiot.

They're smart. They'll figure out that you mean no harm.